Vorayuth Yoovidhya, who is suspected of driving a Ferrari that struck and killed a policeman in Bangkok. Photograph: AP

Thai police are charging the Red Bull energy drink heir with drunk driving after he allegedly killed a police officer while speeding in his Ferrari and fleeing the scene.

Police said on Thursday that tests taken in the hours after Monday's crash showed 27-year-old Vorayuth Yoovidhaya's blood alcohol content was at 0.063, exceeding the legal limit of 0.05. They said the findings could result in a stiffer penalty for Vorayuth, who was originally charged with causing death by reckless driving.

Police said Vorayuth had admitted driving the Ferrari that struck and killed the officer but he said the officer swerved in front of his vehicle. Witnesses said the car dragged the officer's body down the road before speeding away.

Vorayuth's lawyer has said his client was not drinking before the accident.